A data processing device (e.g., a desktop computer, a laptop computer, a notebook computer, a netbook, a mobile device such as a mobile phone) may have a display unit associated therewith. The display unit may be illuminated by a backlight of the data processing device. The display unit may be a component of the data processing device consuming maximum power from a battery thereof. In the case of the data processing device being a mobile phone, a user of the mobile phone may most frequently check a current time displayed on the display unit and/or a remaining battery time without performing any other action on the data processing device. By default, an entire display screen area of the display unit may be illuminated by the backlight, thereby consuming a lot of power from the battery.